Universität Bielefeld

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Chiral reagents and catalysts in organic syntheses


Symmetrical (R2Zn) or mixed diorganozinc compounds (R1ZnR2) smoothly react with a series of nitroolefins in the presence of catalytic amounts of copper(I) salts and provide synthetically versatile nitro compounds in moderate to good yields. Simple alkyl groups, functionalized residues, or mixed trimethylsilylmethyl organozinc compounds (TMSM)ZnR may be employed for conjugate addition, while the TMSM group is not being transferred. Enantiomerically pure copper(I) complexes with BINOL based chiral phosphoramidite ligands efficiently catalyze the addition of dialkylzinc compounds to nitroalkenes. Diethylzinc addition occurs with high yields and excellent enantioselectivity. Nitrostyrene, 3-nitroacrolein dimethylacetal, and 3-nitroacrylates have been used as substrates. The nitroolefin moiety predominates over the acrylate moiety and acts as the more powerful Michael acceptor. 2-Alkyl-3-nitropropanoates are exclusively obtained with excellent yield and enantioselectivity. The products can easily be transformed into β2-homoamino acids, compounds of high relevance for different areas of preparative organic chemistry.



Enantioselective Copper(I) Catalyzed 1,4-Addition of Diethylzinc to Nitroolefins
N. Sewald, V. Wendisch
Tetrahedron: Asymmetry, 9 (1998) 1341-1344.


First Synthesis of a β2 -Homoamino Acid by Enantioselective Catalysis
A. Rimkus, N. Sewald
Org. Lett., 5 (2003) 79-80.


Conjugate Addition of Organozinc Compounds to Nitroolefins
A. Rimkus, N. Sewald
Synthesis (Feature Article), (2004) 135-146.



People involved:
Dr. Audrius Rimkus, Dr. Volkmar Wendisch


Info

Here you find Information about the projects of the workgroup Organic Chemistry III.